The present invention relates to a new process for preparation of resorcinol, using the meta-phenylenediamine hydrolysis reaction. A reactor vessel made of a suitable material such as zirconium or a zirconium alloy is used, thus resisting corrosion and formation of resinous materials.
Resorcinol can be commercially produced by three different processes, namely, alkali fusion of meta-benzenedisulfonic acid, the hydroperoxidation process using meta-diisopropylbenzene, and the acid hydrolysis of meta-phenylenediamine. Since meta-phenylenediamine (MPDA) is commercially available, production of resorcinol is possible in a simple one-step acid hydrolysis process employing MPDA as the starting material. However, the MPDA hydrolysis process requires high temperature and strong acid catalysts. Employing strong acid catalysts in the presence of water brings the pH of the solution to a very low value. The combination of low pH and high temperature make the hydrolysis process dangerous and requires the use of noncorrosive materials to withstand these severe processing conditions.
When the reaction temperature is high, additional problems are encountered using the MPDA hydrolysis process. Resorcinol forms both water soluble and insoluble resinous products, or tars, at elevated temperatures in the presence of strong acids. These resinous products can be the result of resorcinol reacting with other materials present in the reaction mixture, including the starting materials (such as MPDA) or reaction intermediates such as m-aminophenol (MAP). In addition, resorcinol has the tendency to produce polyaryl ether-type structures under these hydrolysis process conditions. The insoluble resinous materials can build up in the reactor, making frequent cleaning necessary. In continuous operations, they can block process lines, resulting in a potentially hazardous situation. Additionally, the formation of resinous products tends to reduce the final resorcinol yield from this process. Therefore, it is important to develop a process that does not produce any resinous or insoluble material during the hydrolysis reaction.
Several attempts have been made in the past to develop a cost-effective and simpler process for the manufacture of resorcinol from the acid hydrolysis of MPDA. For example, U.S. Pat. No. 3,462,497 discloses the hydrolysis of MPDA using ortho-phosphoric acid or H2SO4 in an autoclave fitted with a Monel liner. From the data presented in the examples, it is evident that a resinous-type product was produced during the hydrolysis process.
U.S. Pat. No. 3,862,245 discloses a process to prepare resorcinol from the MPDA hydrolysis using H2SO4 in a tantalum tubular reactor surrounded by an oil bath; a resorcinol yield of 67.5 wt. % was achieved with an H2SO4/MPDA molar ratio of 1.6:1.
Japanese Patent Disclosure S52-153919 discloses that a very high resorcinol yield can be achieved with hydrochloric acid in a Hastelloy B type reactor. Use of H2SO4 resulted in a significant decline in resorcinol yield.
U.S. Pat. No. 3,862,246 discloses the use of ammonium bisulfate as an acid for the hydrolysis of MPDA to produce resorcinol. Use of large amounts of salt is uneconomical and results in handling difficulties during the manufacturing process.
There is a continued need for the development of a simple and cost-effective method of preparing resorcinol, using the MPDA hydrolysis reaction.
The present invention solves the above need by providing a method of making resorcinol using the MPDA hydrolysis process, in a reactor vessel made of zirconium, a zirconium alloy or other suitable material as will be defined herein. Sulfuric acid and meta-phenylenediamine in an aqueous solution are placed in the reactor vessel and heated, while stirring, for a period of time sufficient to complete the hydrolysis reaction and then cooled to room temperature. After cooling, the resorcinol can be extracted from the aqueous solution with an organic solvent. It has been found that a zirconium or zirconium alloy reactor vessel is particularly resistant to corrosion and able to withstand the severe processing conditions required by the MPDA hydrolysis process. Other materials, such as gold, molybdenum, platinum, titanium, and tungsten, as well as alloys containing these materials, are also expected to provide corrosion resistance along with the ability to withstand the severe processing conditions. This reduction in corrosion contributes to the reduction of tarry, resinous materials, because metal corrosion products which can catalyze the formation of the tarry residue are not present in the reactor vessel. Additionally, use of stirring during the heating process, in combination with the proper molar ratios of H2SO4 and MPDA, further limits the formation of resinous materials.
It is an object of the present invention, therefore, to develop a cost-effective resorcinol manufacturing process using the MPDA hydrolysis reaction.
It is an additional object of the present invention to improve the resorcinol yield using the MPDA hydrolysis reaction.
It is an additional object of the present invention to use the MPDA hydrolysis reaction with a suitable reactor vessel to avoid corrosion and formation of tar or other resinous by-products during the hydrolysis reaction.
These and other objects will be more fully understood from the following detailed description, examples and appended claims.